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Recent functional brain imaging studies have shown that sensory-specific brain regions that are activated during perception/encoding of sensory-specific information are reactivated during memory retrieval of the same information. Here we used PET to examine whether verbal retrieval of action phrases is associated with reactivation of motor brain regions if the actions were overtly or covertly performed during encoding. Compared to a verbal condition, encoding by means of overt as well as covert activity was associated with differential activity in regions in contralateral somatosensory and motor cortex. Several of these regions were reactivated during retrieval. Common to both the overt and covert conditions was reactivation of regions in left ventral motor cortex and left inferior parietal cortex. A direct comparison of the overt and covert activity conditions showed that activation and reactivation of left dorsal parietal cortex and right cerebellum was specific to the overt condition. These results support the reactivation hypothesis by showing that verbal-explicit memory of actions involves areas that are engaged during overt and covert motor activity., (Copyright 2001 Academic Press.)

In three experiments, we studied memory for action events with respect to exceptions from the Tulving-Wiseman function demonstrated in experiments on recognition failure of recallable words. In Experiment 1, we examined exceptions of poor integration in a regular recognition failure condition (i.e., recognition of targets without contextual cues, followed by recall of targets in the presence of contextual cues). In Experiment 2, we examined exceptions of cue overlap in which subjects also had access to the information of contextual cues at recognition test. In Experiment 3, we attempted to equate the levels of recognition across the action and verbal encoding. In addition, the cue overlap and no-cue overlap conditions were studied in a within-subjects design. Results from the three experiments indicated that encoding enactment (episodic integration) and conceptual integration (semantic integration) are related to each other. As a consequence of this relationship, there is a larger independence between recognition and recall of well-integrated items with encoding enactment. On the other hand, for the poorly integrated items without encoding enactment, there is a larger dependence between recognition and recall. Even in the cue overlap condition, where there is a case of large dependence between recognition and recall, the same pattern of data was observed. The results are discussed in terms of an episodic integration view of encoding enactment.

One experiment compared the effect of elaboration on enacted and non-enacted events. The commands were either presented in a basic form (e.g., "wave your hands") or in an enriched form. The commands were enriched by adding statements to the commands of how to perform the actions (e.g., "wave your hands as a conductor"). Free- and cued-recall data showed elaboration to have a dissociative effect on enacted and non-enacted events. Memory for the non-enacted events benefited from enrichment, whereas simple enacted events were remembered to a higher extent than complex enacted events. Lack of benefit from elaboration on memory of enacted events is suggested to be due to enactment leading to a sufficient degree of item-specific processing, and a negative effect of elaboration is suggested to occur when the way of manipulating item complexity decreases the familiarity of the actions. Familiarity ratings of the items by two independent groups of subjects supported this interpretation.

When subjects study a list of B items paired with A items and are tested for recognition of the B items alone, and then for recall of the B items given the A items as cues, B items that can be recalled frequently go unrecognised. The extent of this recognition failure is predictable from a function discovered by Tulving and Wiseman (1975), which relates the probability of recognising the recallable items to the probability of recognising all items. Two kinds of exceptions to this function have been discovered: encoding exceptions and retrieval exceptions. Very few observations of retrieval exceptions exist. Four experiments described in this article provide further evidence that such exceptions occur when the B items are categorised and the A items are the names of the categories. According to a contextual account of the function and exceptions to it, these retrieval exceptions occur because the information provided by the A-item cues can be largely retrieved from the B items in the recognition test; hence, as cues, the A items do not provide much different contextual information to that provided by the B items. By this account, the function is an empirical law; exceptions fall outside the range of this law and define its boundary conditions.

Enactment during the encoding of simple imperatives has been found to improve substantially performance on conceptually driven explicit-memory tests. In two experiments the effect of this manipulation on a conceptually driven implicit test (category association) was studied. A conceptually driven explicit test (free recall) was also included. In Experiment one three different study conditions (enactment with real objects, reading, and generation) were considered. In Experiment two there were two study conditions (enactment with imaginary objects and reading). Compared to reading, generation was found to improve the performance on both free recall and category association, whereas enactment affected free recall only. In a final experiment subjects imagined that they performed the tasks, and this manipulation was found to improve the memory performance on both tests. Taken together, this pattern of results is interpreted as suggesting that free recall and category association have a process in common that is sensitive to semantic processing at study (promoted by generation and imagery, but not by enactment), and that free recall involves a retrieval process in addition that is facilitated by a rich encoding environment (provided by enactment).

Two experiments were designed to test a claim made by Gardiner (1988) that there are generation effects in implicit memory as measured by word-fragment completion. Subjects either read words at study or generated the words from fragments. As in previous research, fragments were completed to a greater extent if they were identical at study and test than if they differed. In Experiment 1 it was found that subjects could recognize explicitly the exact form of fragments that had been used for self-generation and distinguish these from other forms of fragments. An analysis of the contingency relations between recognition of fragments and fragment completion showed a high degree of dependence between the two tests. In Experiment 2 it was found that the match of surface features between study and test was a necessary, but not sufficient, condition to produce enhancement of priming. The results are interpreted as supporting the claim that generation does involve a data-driven component in addition to semantic elaboration.

The ability of patients with Alzheimer's disease (AD) to utilize semantic category cues in order to improve memory performance was examined. Categorizable lists of words or objects were presented under five different encoding conditions: (a) nouns, (b) objects, (c) objects with a semantic orienting question, (d) objects with self-generated motoric acts, and (e) objects with experimenter-instructed motoric acts. Subjects were asked to memorize the items for a free recall test, and were subsequently provided with the category names in a cued recall test. Mildly, moderately, and severely demented AD patients, and a group of normal older adults participated in the study. Results showed that normal older adults and mildly demented AD subjects were able to utilize cues to improve memory performance in all conditions. Moderately demented patients utilized cues in all conditions except in the verbal condition (condition [a]), whereas severely demented patients utilized cues only in the motoric condition (condition [e]). These results suggest that the ability to utilize category cues following a motoric encoding is preserved later in AD than the ability to utilize cues after a semantic encoding.

Dichotic listening tests were used to determine cerebral hemisphere memory functions in patients with complex partial seizures before, 10 days after, and 1-3 yr after right (RTE) or left (LTE) temporal-lobe excisions. Control subjects were also tested on two occasions. The tests consisted of presenting a series of 12-word lists and 7-word lists alternately to the two ears while backward speech was presented to the other ear. Measures of immediate free recall, final free recall, final cued recall, and serial recall were employed. The results revealed: (a) that both groups of patients were inferior the control group in tests tapping long-term memory functions rather than short-term memory functions, (b) a right-ear advantage for RTE patients at postoperative testing, (c) that the LTE group was more affected by surgery than the RTE group, and (d) a general improvement in recall performance from early to late postoperative testing. Taken together, these results indicate that the present dichotic test can be used as a non-invasive hemisphere memory test to complement invasive techniques for diagnosis of patients considered for epilepsy surgery.

A total of 219 patients who had suffered from subarachnoid haemorrhage (SAH) were given a set of memory tests. The tests comprised immediate free recall (indexing long-term memory, LTM, and short-term memory, STM), final free recall (LTM) and final cued recall (LTM) of words as well as a digit-span test (an index of working memory, WM). STM was highly sensitive to brain damage caused by SAH whereas WM was not. Localisation of the ruptured aneurysm, angiographic vasospasm or mass effect did not have any selective influence on the SAH group's STM or WM. The final free recall test was the most sensitive measure of LTM whereas the LTM part of the immediate free recall test was the least sensitive. LTM impairment was most pronounced for patients with ruptured left anterior communicating artery aneurysms or for patients with angiographic vasospasm or mass effect. It is suggested that, in the SAH patients, a passive phonological short-term store is impaired, but the active maintenance rehearsal mechanism is intact. For patients with LTM dysfunction, deeper, more elaborate, active processing is disrupted, hindering efficient long-term storage.